It is well known that commercial moldings of complex shape made from mineral reinforced polyamides such as those discussed in U.S. Pat. No. 3,843,591 often have a variety of visual surface blemishes. These blemishes may occur in parts where appearance is important, for example, power tool housings, automotive exterior parts, handles and the like. In laboratory testing of mechanical properties of such mineral reinforced polyamides a single gated test bar is commonly used and the visual surface blemishes appear as a dull area around the mold gate. These blemishes are commonly referred to as "gate smear".
It is also well known that in commercial molding operations it is desirable to use minimum cycle times to achieve maximum product rates and to fill molds without premature freezing of the polymer. In conventional mineral reinforced polyamides, as cycle time is reduced, the tendency for "gate smear" blemishes is increased. It is also understood that the lower the mineral content of the resin, the less tendency there is to form such blemishes.
During the course of work to try to improve the toughness of mineral reinforced polyamides by using toughening agents such as those described in U.S. Pat. Nos. 4,174,358 and 3,848,163 and British Pat. No 998,439 it was found that certain selected toughening agents had an unexpected effect in dramatically reducing gate smear blemishes.